Hello

Our oldest tandem a Dawes Duet has sentimental value so we have kept it to go shoping, plug along tracks and such like.

The transmission was always a bit iffy - the rear derallieur in particular has always been slow and inconsistent. I have tried various things with cables etc but have now decided that it is time to give the bike a bit of a makeover.

At the Eroica last weekend we saw a tandem running an SRAM 1x system. I have a bike that runs this system and love the linearity without having to worry about crossover point like with a double/triple (and we all know how temperamental a flont changer can be).

So this thread is about cheaply upgrading my Dawes to just have a rear changer with  a big freewheel.  I have discussed the viability of this with several regulars on here (John and Martyn). Martyn was concerned about gear range at the top end but given the use of this tandem I can forego that (like many of you we have another tandem we can go fast on).

The bike currently has sychronisation chain on one side and triple chainset to seven speed on the other (although I have changed the wheels and used a spacer so the freehub body will support 10 speed). I am planning to move to double chainset with synchronisation chain on the same side as transmission (easier to transport given we lie it down in the car). 

My questions are:

1. How do I work out the bottom bracket length I need? - Is it just the length for a double chainset recommended for the cranks I am going to buy?

2. Are there any gotchas with changing the side of the synchronisation chain?

3. Will tensioning the synchronisation chain still work the same?

4. I am proposing to use an ordinary chainset on the rear drive not SRAM's specially toothed one. But given I am just going to run a normal 10 speed set up are there any problems with this?

5. Any questions I should have asked?